This disclosure relates to a method for treating a subterranean well formation to stimulate the production of hydrocarbons and, more particularly, such an apparatus and method for fracturing and squeezing the well formation.
Several techniques have evolved for treating a subterranean well formation to stimulate hydrocarbon production. For example, hydraulic fracture methods have often been used according to which a wellbore penetrates the formation to be stimulated, packers are installed to isolated a zone in the formation, and a stimulation fluid containing acids, gels, sand slurry, and the like, is pumped through the wellbore and discharged, usually through a jetting tool, or the like, at a relatively high velocity into the isolated portion of the formation. The pressurized stimulation fluid pushes against the formation at a very high force to establish and extend cracks on the formation.
Also, squeezing methods have been used which involve introducing stimulation fluids containing acids to the formations at a pressure that is higher than the formation pressure (but not as high as the fluid pressure in the fracturing methods), causing the fluid to infiltrate the pores in the formation and react with the formation to enlarge the pores. Since these stimulation fluids are usually very reactive, especially at elevated temperatures, the fluid is often prematurely spent close to the wellbore in the formation. Thus, no extended reach is achieved and the fluid-entry point is often greatly enlarged. As a result, it is difficult to form multiple, relatively long and effective acid fingering throughout the wellbore face, especially in low-permeability reservoirs that require deep penetration.
Additional problems encountered in these types of operations occur when the operation is carried out in relatively large diameter wellbores or casings, especially when the jetting tool has a relatively small diameter which is required when it is connected to relatively small diameter tubing, and/or when the tool has to be passed through relatively small diameter production tubing. In these situations, the tool, after being lowered to the proper height in the wellbore, is spaced a considerable distance from the inner surface of the wall of the wellbore or casing. Thus, the jetting effect is diminished, especially in connection with the squeezing methods discussed above, due to the fact that the jetted fluid has to travel a relatively long distance to the wall. In addition, the reaction forces caused by the jets tend to push the tool away from the wall; thus increasing this distance even further.
Therefore, what is needed is a stimulation treatment according to which the need for isolation packers is eliminated, the depth of penetration is improved, premature reaction of the acid with the formation is prevented, and the disadvantages of relatively small diameter jetting tools are eliminated.